Ambient Phosphor with High Efficiency and Long Lifetime in Poly(Methyl Methacrylate) Through Charge‐Transfer‐Mediated Triplet Exciton Formation for Photolithography Applications

• Published in: Angewandte Chemie International Edition 2024-01, Vol.63 (4), p.e202312534-n/a
• Main Authors: Liu, Ruyi, Liu, Chuanhao, Fu, Caixia, Zhu, Zhenzhen, Chen, Kuan, Li, Chuan, Wang, Lingjie, Huang, Yan, Lu, Zhiyun
• Format: Article
• Language: English
• Subjects: Ambient Phosphorescence; Charge transfer; Defect Indicator; Excitons; High Efficiency; Long Lifetime; Organic compounds; Phosphorescence; Phosphors; Photolithography; Polymethyl methacrylate; Polymethylmethacrylate; Polyvinyl alcohol
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202312534

Currently, purely organic compounds showing ambient phosphorescence with high efficiency (ΦP) and ultra‐long lifetime (τP) are quite rare and often need to be achieved in hydrophilic poly(vinyl alcohol)‐based hosts. This severely limits their applications. Here, we provide a solution to this issue by constructing an ortho‐linked donor‐acceptor (D−A) dyad whose D moiety has not only a long‐lived T1 state to achieve a long τP, but also a Tn state that is close to the S1 state of the dyad to trigger effective spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). The rationality of this strategy was validated by a new phosphor OF‐BCz that is able to show a τP of 1.92 s and a ΦP of 30 % even in a less rigid matrix of poly(methyl methacrylate) (PMMA). Excitingly, OF‐BCz exhibited its potential as both a photocuring initiator and an in situ quality indicator, allowing for the visual detection of defects in photolithographic patterning. Through spin‐orbit charge transfer intersystem crossing (SOCT‐ISC) strategy, a new ortho‐linked donor‐acceptor dyad OF‐BCz showing a long lifetime (τP) of 1.92 s and a high efficiency (ΦP) up to 30 % in PMMA matrix, was constructed. Thanks to its excellent performance and high triplet energy level (ET1), OF‐BCz was successfully applied in photolithography as a photoinitiator and an in situ quality indicator.